Hal, who returned to play last season after undergoing treatment for Hodgkin lymphoma that was diagnosed in May, said in his message that his decision was not related to his health.
Thank you Houston pic.twitter.com/doc4ONMKRA— Andre Hal (@Drehal29) April 2, 2019
Hal, 26, ended up playing in eight games last season and finished with three interceptions.
Drafted in the seventh round (216th overall) by the Texans in 2014, he appeared in 69 games (40 starts) for Houston and had 12 interceptions, 31 passes defensed, two forced fumbles, a sack and 189 tackles.
"Andre Hal is the epitome of what it means to be a Houston Texans player. What he overcame last season is nothing short of incredible and is an inspiration to every single person in this building," Texans coach Bill O'Brien said in a statement. "Over the last five years, Andre's leadership, infectious personality in the locker room and play-making skills on the field were instrumental to our success. He's what this place is all about. Although Andre will be missed, I have no doubt that he will be extremely successful in the next chapter of his life."
Hal was expected to back up new safety Tashaun Gipson and 2018 draft pick Justin Reid in 2019. Last season, he played in more than 42 percent of the Texans' defensive snaps in five of the regular-season games he played in.
ESPN's Sarah Barshop contributed to this report.